A gas turbine system for a power generation system typically includes a gas turbine engine, a generator operatively coupled to the gas turbine engine, an air inlet system, and an exhaust system for receiving exhaust gas from the gas turbine engine. The exhaust outlet portion of the gas turbine is connected to an exhaust plenum of the exhaust system in such a way to provide a seal so that no exhaust leaks to the outside or ambient air through the connection. To this end, flex seals for sealing the exhaust plenum to the gas turbine are secured to a forward wall of the exhaust plenum. The forward wall includes thermally conductive continuous rolled attachment bars for attaching the flex seals to the forward wall. In one conventional exhaust plenum, these attachment bars are uninsulated and exposed to the hot exhaust gas flowing inside the exhaust plenum. The inventors of the present invention have identified the uninsulated attachment bars as being possible points of failure of the exhaust plenum because the threaded bars are heated to a different temperature than the exterior shell of the forward wall, and the resulting thermal differential leads to deformation, and possibly failure, of the exhaust plenum.
In one conventional exhaust plenum, the forward wall and an aft wall each include upper and lower wall sections that are secured to one another by flange plates extending outward from exterior surfaces of the respective upper and lower wall sections. A high temperature cloth gasket is installed between the flange plates. The inventors of the present invention have identified these conventional flange plates as being a possible point of failure of the exhaust plenum because thermal expansion of the attachment bars causes the flange plates to separate and the flex seals to buckle, which leads to exhaust gas leaking from the exhaust plenum.